Computer systems execute various types of software applications. Many of these software applications, known as “sub-applications,” are created to provide specific functionalities to other, more comprehensive applications, known as “shell applications.” For this reason, shell applications are said to “host” one or more sub-applications. For example, an electronic mail (e-mail) software program (e.g., MICROSOFT® OUTLOOK®) may use a plug-in to encrypt and decrypt e-mail messages. In such cases, the e-mail software program is referred to as the shell application, while the encryption and decryption plug-in is referred to as the sub-application. In another example, an operating system (OS) may use a word processing application and a spreadsheet application. In such cases, the OS is referred to as the shell application, while the word processing and spreadsheet applications are referred to as the sub-applications. In general, any application that hosts another application as described above may be referred to as a “shell application.” Thus, a shell application may include an application that runs under an OS or may even include the OS itself. Similarly, any application that is hosted by another application may generally be referred to as a “sub-application.”
Sub-applications do not operate independently of shell applications. Instead, sub-applications interact with a shell application using “services” provided by the shell application. These services provide the sub-applications with the protocol the sub-applications require to communicate with the shell application and to provide their respective functionalities to the shell application. If the services of the shell application are not available, the sub-applications are unable to operate. The sub-applications are thus said to be “dependent” on the shell application. Such dependency is undesirable because the process by which sub-applications are developed to be compatible with shell applications is costly, tedious and time-consuming.
Both the shell application and the sub-applications generate graphical data to be displayed on a system display. Because sub-applications are dependent on the shell application, both sub-application graphical data and shell application graphical data are displayed using a single graphical user interface (GUI) of the shell application. As explained above, elimination of the interdependency between shell applications and sub-applications is generally desirable. However, such elimination prevents the display of sub-application graphical data using the shell application's GUI. Thus, the sub-applications are left without an effective means by which to display their graphical data.